1. Field of the Invention
The present invention relates to a punching die using a gaseous spring.
2. Description of the Related Art
In the conventional punching die, a punch body movable up and down is fitted to a punch guide, and further a spring such as a coil spring, a disk spring, a urethane spring, etc. is interposed between the retainer collar and a punch head fixed to the upper portion of the punch guide.
In the above-mentioned conventional technique, however, when the spring is assembled between the retainer collar and the punch head, there exists a problem in that the spring must be deformed to some extent and a strong force is required to deform the spring for assembly. In addition, when the cutting edge of the punch body is required to be ground again, the retainer collar, the punch head and the spring must be all disassembled. In this disassembly operation, since some parts are tightly assembled or fitted from the standpoint of the punch head structure, it is not easy to disassemble these parts.
Further, after the cutting edge of the punch body has been ground again, the length of the assembled punch body must be adjusted. In this case, since a strong force is required for assembly, there exists a problem in that the adjustment operation is not easy.